Generally, a fire extinguisher is provided with a pressure gauge and a pressure indicator, and an inspector has to check the pressure indicator for confirming whether the fire extinguisher is normal. A building usually has a lot of fire extinguishers usually placed at multiple locations, and the fire extinguishers should be inspected periodically to ensure that they can function normally. Therefore, the inspector needs to directly check the pressure indicators of the extinguishers one by one by going through all the locations where the fire extinguishers are placed, and this may consume a lot of manpower.